Shaft connection

ABSTRACT

A shaft connection  1  for a longitudinal shaft assembly, has at least a first shaft having a first and second ends, and a second shaft, disposed so as to be coaxial with the first shaft, having first and second ends; the shafts extending axially. The first end forms a hollow portion. The first shaft end forms a first journal having a displacement portion. The first shaft end at least in an initial position of the shaft connection extends through the hollow portion which axially by the displacement portion forms a guide portion and circumferentially forms a form-fitting first connection. In the initial position a mutual axial displacement of the first and second shafts is prevented by an axial securing feature. In a crash the axial securing feature; is releasable by an axial release force. The first shaft is axially displaceable relative to the second shaft.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a national stage of, and claims priority to, PatentCooperation Treaty Application No. PCT/EP2017/083309, filed on Dec. 18,2017, which application claims priority to German Application No. DE 102017 100 356.8, filed on Jan. 10, 2017, which applications are herebyincorporated herein by reference in their entireties.

BACKGROUND

A longitudinal shaft assembly generally extends along a vehiclelongitudinal axis in order for a drive input side of the motor vehicleto be connected to a drive output side of the motor vehicle. Thelongitudinal shaft assembly is typically used for transmitting a torquefrom the drive input (for example the motor and/or transmission) to thedrive output (for example the differential, the axle gearbox,transmission) of the motor vehicle. When the drive input is installed inthe front region of the motor vehicle, the longitudinal shaft assemblytransmits the torque to the rear wheels, or when the drive input isdisposed in the rear region of the motor vehicle the longitudinal shaftassembly transmits the torque to the front wheels, respectively.

Longitudinal shaft assemblies in the motor vehicle represent a rigidconstruction which is to be designed in particular in terms of the crashbehavior thereof. It is therefore a substantial focal point in thedesign of longitudinal shaft assemblies that no component of thelongitudinal shaft assembly is released from the longitudinal shaftassembly in such a manner that said component would penetrate otherregions of the vehicle. It is thus in particular to be avoided thatparts of the longitudinal shaft assembly penetrate into the passengerinterior space and/or the fuel tank, on account of which an additionalrisk of injury to vehicle occupants or a risk of fire on account ofescaping fuel could arise. It is furthermore to be ensured that thelongitudinal shaft assembly during a deformation in the event of a crashabsorbs the deformation energy (only) to the desired extent and inparticular in a continuous manner.

Such longitudinal shaft assemblies at least have a first shaft and asecond shaft by way of which the torques of the drive input of the motorvehicle are transmitted. The longitudinal shaft assembly herein by wayof constant velocity rotary joints can be linked to further componentsof the motor vehicle, said constant velocity rotary joints preferablypossessing a limited displacement range in an axial direction. Onaccount of the displacement range of the constant velocity joints, themovements of individual components of the longitudinal shaft assembly orof the motor vehicle that arise in the usual operation of thelongitudinal shaft assembly are compensated for in the longitudinaldirection of the vehicle (the axial direction). Moreover, torsioning ofthe longitudinal shaft assembly on account of the constant velocityjoints in relation to further components of the motor vehicle that alsoarises in the operation is equalized by the constant velocity joints bydeflecting the constant velocity joints. The displacement range and thepivoting region of the longitudinal shaft assembly are designed so as tobe specific to the application and are limited. Specifically in theautomotive sector, a displacement range of the longitudinal shaftassembly of (in total) 20 mm to 80 mm (millimeters) can be assumed, forexample. In the same type of application, a pivoting range of 0° to 4°,or even up to 8° (angle degrees) can be assumed, respectively.Considering the displacement distance of a constant velocity joint ofthe longitudinal shaft assembly, a displacement range of the oneconstant velocity joint of 10 mm to 40 mm (millimeters) thus resultshere for the same type of application, for example.

Longitudinal shaft assemblies of the type mentioned above are to bedesigned for the respective type of use, in particular in terms of thedrive force to be transmitted. Further parameters are inter alia:construction length of the longitudinal shaft assembly, spaceavailability in the motor vehicle, weight of the motor vehicle, crashrequirements.

A longitudinal shaft assembly in which the first shaft in the event of acrash is pushed into the tubular and correspondingly hollow second shaftand the longitudinal shaft assembly is thus compressed is known from DE10 2008 048 388 A1.

SUMMARY

The present disclosure relates to a shaft connection, in particular fora longitudinal shaft assembly of a motor vehicle. A shaft connection isdisclosed which in the event of a crash, e.g., as simulated by vehiclecrash experiments, or component crash experiments, respectively, of thelongitudinal shaft assembly or the shaft connection, respectively,proceeding from an initial position in the operation of the shaftconnection, can be elongated and compressed without the mutual guidingof the first shaft and the second shaft being sacrificed. The guidingguaranteed in the case of the compression and also in the case of theelongation of the shaft connection is intended to prevent any deflectionof individual components of the longitudinal shaft assembly in the eventof a crash.

The features set forth in the claims are specified and explained in moredetail in the description, wherein further preferred embodiments of theinvention will be illustrated. Further, advantageous embodiments of theshaft connection are set forth in the independent and dependent claims.It is to be pointed out that the features individually listed in thedependent claims can be combined with one another in a technologicallyexpedient manner and define further embodiments.

A shaft connection (in particular the shaft connection of a longitudinalshaft assembly of a motor vehicle) contributes to this end, said shaftconnection at least having a first shaft having a first end and a secondend, and a second shaft, disposed so as to be coaxial with the firstshaft, having a first shaft end and a second shaft end; wherein theshafts extend along an axial direction. The first end of the first shaftforms a hollow portion; wherein the first shaft end of the second shaftforms a first journal having a displacement portion; wherein the firstshaft end at least in an initial position of the shaft connectionextends through the hollow portion, and the hollow portion by way of thedisplacement portion along the axial direction forms a guide portion andin a circumferential direction forms a form-fitting first connection. Inthe initial position which is present in particular in the operation ofthe shaft connection in an installed situation, for example as part of alongitudinal shaft assembly in a motor vehicle or on a testbed, a mutualdisplacement of the first shaft and the second shaft along the axialdirection is prevented by an axial securing feature. In an (actual orsimulated) event of a crash, the axial securing feature is releasable byway of a release force that acts in the axial direction, and the firstshaft is displaceable along the axial direction in relation to thesecond shaft. Proceeding from the initial position, guiding by the guideportion is guaranteed in the case of an elongation as well as in thecase of a compression of the shaft connection.

In particular, a deflection of the shafts in the event of a vehiclecrash in which, proceeding from the initial position, first anelongation (thus an extension in length in the axial direction) of theshaft connection and only thereafter a compression (thus shortening inthe axial direction) of the shaft connection is performed can thus beprevented on account of maintaining the mutual guiding of the shafts.

The elongation is performed in particular by repositioning of themotor-transmission unit disposed in the region of the front of thevehicle in the travelling direction as a result of a crash event. Thisrepositioning can be enabled, for example, by way of a soft enginemounting. In the event of a crash, the motor-transmission unit by virtueof the soft mounting is thus initially repositioned towards the front,while a linkage of the longitudinal shaft assembly, for example to arear axle, is almost rigid such that the longitudinal shaft assembly iselongated. The compression during which the mutual guiding of the shaftsis likewise to be guaranteed is now performed only after saidelongation.

The longitudinal shaft assembly is preferably disposed so as to besubstantially parallel to a vehicle longitudinal axis of a motorvehicle, wherein deviations of less than 10 angle degrees are includedherein.

Proceeding in each case from the initial position, the form-fittingfirst connection in the case of the elongation as well as in the case ofthe compression of the shaft connection is in particular guaranteed atleast over a distance of 20 millimeters, preferably of 30 millimeters.Proceeding from the initial position, the form-fitting first connectionin the case of an elongation is in particular guaranteed at least in thecase of the elongation over a distance of at least 60 millimeters, inparticular of at least 80 millimeters.

In particular, the form-fitting first connection (in relation to thecircumferential direction) in the initial position has a length in theaxial direction, wherein it is guaranteed in the case of an elongationof the shaft connection by a displacement of at least 20 millimetersacross the displacement portion that the length of the first connectionis maintained to the extent of at least 20% of the length.

In particular, the displacement portion in the axial direction extendsso as to be longer than the hollow portion such that the displacementportion at least in the case of an elongation, optionally also in thecase of a compression, of the shaft connection can guarantee the lengthof the first connection as provided in the initial position. Inparticular, an extent of the displacement portion (and in particular anextent of the profiled feature configured thereon for producing thefirst connection) along the axial direction is at least 120%, preferablyat least 150%, of the extent of the hollow portion (and in particular anextent of the profiled feature configured thereon for producing thefirst connection).

The form-fitting first connection in the initial position preferably hasa length in the axial direction. In particular, the displacement portionis at least partially moved out of the hollow portion in the case of anelongation of the shaft connection. The form-fitting first connectionherein is now to be maintained in particular by the displacement portionwhich along the axial direction in particular extends across a largerlength than the hollow portion, at least in the case of an elongation ofthe shaft connection. It is in particular to be guaranteed by way of thedisplacement portion that the length of the form-fitting firstconnection present in the initial position at least in the case of anelongation (optionally also in the case of a compression) of the shaftconnection is maintained at a displacement of at least 20 millimeters,preferably at least 30 millimeters, particularly preferably at least 60millimeters, or even at least 80 millimeters, proceeding from theinitial position, or at least is maintained to the extent of 20% of thelength, in particular at least to the extent of 50% of the length,preferably at least to the extent of 75%, or even at least to the extentof 90% of the length.

Form-fitting connections are created by the mutual engagement of atleast two connection partners. On account thereof, the connectionpartners cannot be released even in the absence of a force transmissionor in the case of an interrupted force transmission. In other words, inthe case of a form-fitting connection the one connection partner is inthe way of the other.

In particular, the form-fitting first connection is formed by a splinetoothing on the displacement portion and on the hollow portion.

The second shaft, proceeding from the displacement portion and towardsthe second shaft end, preferably has a journal portion that extendsalong the axial direction, wherein a largest diameter of the journalportion is smaller than a smallest diameter of the hollow portion. Inparticular, the journal portion extends along the axial direction acrossa length of at least 20 millimeters, e.g., of at least 40 millimeters,or in a further example of at least 100 millimeters.

In particular, the largest diameter of the journal portion differs fromthe smallest diameter of the hollow portion by at most 2%, preferably byat most 1%. The journal portion is in particular distinguished in thatsaid journal portion has a largest diameter defined in such a manner.

This embodiment of the journal portion enables the second shaft to beable to be pushed further into the first shaft so that the hollowportion by way of the journal portion guarantees mutual guiding of theshafts. In particular, mutual guiding of the first shaft and the secondshaft thus continues to be guaranteed in the case of a furthercompression of the shaft connection, even when the form-fitting firstconnection is no longer present.

In particular, the second shaft in the region of the first shaft end hasa detent which for delimiting the mutual displacement in the case of anelongation of the shaft connection interacts with the first shaft, inparticular with a second hollow portion end of the first shaft. In thecase of an elongation of the shaft connection, the detent on the secondshaft, conjointly with the first shaft, delimits any further elongationof the shaft connection. In particular, it is thus prevented that thesecond shaft can be completely removed from the hollow portion of thefirst shaft. It is preferably thus also prevented that the form-fittingfirst connection can be released in the case of an elongation.

The detent is in particular formed by a detent diameter which is largerthan the smallest diameter of the hollow portion, or is larger than asmallest diameter of the first shaft in the region of the second hollowportion end, respectively.

It is in particular guaranteed for assembling the shaft connection (byway of a corresponding selection of the respective diameters of thefirst shaft and the second shaft) that the first shaft can bepush-fitted onto the second shaft by way of the second shaft end of thesecond shaft.

A constant velocity joint having a joint internal part, a joint externalpart, and roller members disposed therebetween is preferably disposed onthe second shaft end of the second shaft, said roller members in theoperation of the longitudinal shaft assembly being mutually disposed ina functional position; wherein a release force required for releasingthe axial securing feature is lower than a force which is required forreleasing the functional position.

The functional position is a disposal of the mentioned components of theconstant velocity joint in a mutual position in which the envisagedfunction of the constant velocity joint is provided (thus thetransmission of torques at a constant velocity of the shafts connectedby way of the constant velocity joint, optionally while deflecting;optionally the axial displacement of the joint internal part in relationto the joint external part when the constant velocity joint is aconstant velocity displacement joint). In particular, the functionalposition is not present when the components, for example in the event ofa crash, have been moved out of said position and a constant velocity ofthe shafts connected by way of the constant velocity joint (in the caseof deflection of the shafts) is no longer guaranteed, for example.

In particular, the shaft connection is constructed such that in theevent of a crash the axial securing feature is initially released andreleasing of the functional position of the constant velocity joint isperformed only thereafter. The mutual guiding of the shafts can thus beguaranteed specifically in the case of an elongation of the shaftconnection and also in the case of a compression, without the providedconstant velocity joints having to be equipped with a correspondingdisplacement capability.

According to one example of the shaft connection, the axial securingfeature comprises an elastically deformable securing ring which in theinitial position is positioned in a first groove (embodied so as to beencircling in the circumferential direction) that is disposed in thehollow portion and in a second groove (embodied so as to be encirclingin the circumferential direction) that is disposed in the displacementportion such that the securing ring in the axial direction forms aform-fitting second connection of the first shaft to the second shaft.

In particular, when assembling the second shaft in the first shaft, thesecuring ring is disposed in the second groove and is then, conjointlywith the displacement portion, introduced into the hollow portion. Thesecuring ring is elastically deformed herein and slides along theinternal circumferential face of the hollow portion until the initialposition is reached. The deformation of the securing ring is reversed inthis mutual position of the shafts, and said securing ring is nowadditionally disposed in the first groove such that a form-fittingsecond connection of the shafts is formed.

In particular, the hollow portion, proceeding from the first end of thefirst shaft towards the second end, along the axial direction extendsfrom a first hollow portion end to a second hollow portion end, whereinthe first groove is disposed on the second hollow portion end; inparticular at a spacing of at most 5 millimeters from the second hollowportion end.

In particular, the hollow portion, proceeding from the first end of thefirst shaft towards the second end, along the axial direction extendsfrom a first hollow portion end to a second hollow portion end, whereinan annular seal is disposed on the first hollow portion end, wherein theannular seal in the initial position, conjointly with the second shaft,effects sealing of the first shaft. The annular seal is in particular aknown O-ring.

The annular seal is preferably positioned in a third groove that isdisposed in the displacement portion.

In particular, the first shaft is a hollow shaft having a cavity thatadjoins the hollow portion, wherein the second shaft in the case of acompression of the shaft connection extends into the cavity.

In particular, the axial securing feature in relation to a compressionof the shaft connection has a release force of at most 30,000 Newtons,preferably at most 20,000 Newtons.

The axial securing feature in relation to an elongation of the shaftconnection preferably has a release force of at most 120,000 Newtons,particularly preferably at most 100,000 Newtons.

The proposed shaft connection for a longitudinal shaft assembly permitsan elongation of the longitudinal shaft assembly without the constantvelocity joints that are in particular disposed at the ends of thelongitudinal shaft assembly being damaged and being deprived of theguiding function of the latter in relation to the shafts. A dynamicrelease force for the elongation has in particular an impulse energy of10 to 1000 Joules, preferably of at most 100 Joules and particularlypreferably of 20 to 50 Joules, wherein an impulse energy of this type ispresent in the event of a crash, for example. The force peak generatedherein should in particular be lower than the breaking force of therespective joint (thus in particular lower than 30,000 Newtons or lowerthan 120,000 Newtons, respectively). The axial securing feature isreleased and a component of the joint (for example the cage) isspecifically not damaged on account of this release force. A subsequent(to the elongation) controlled compression of the longitudinal shaftassembly is thus in particular possible, wherein the release force forthe compression here no longer relates to an axial securing feature(since the axial securing feature in this case has already been overcomein the elongation).

A longitudinal shaft assembly for a motor vehicle is furthermoredisclosed, said longitudinal shaft assembly at least having a firstshaft and a second shaft which form (exactly) one proposed shaftconnection. Proceeding from the initial position, guiding by the guideportion of the shaft connection in the event of a crash is guaranteedboth in the case of an elongation as well as in the case of acompression of the shaft connection.

In particular, the first shaft also at the second end of the first shaftof the longitudinal shaft assembly is connected to a further secondshaft by way of a shaft connection. The explanations above pertaining tothe shaft connection apply here in an analogous manner, in particularalso to the further second shaft.

In the event of a crash, in particular in the context of a crashexperiment of the motor vehicle or of only individual components,preferably in the case of a frontal crash (EURO NCAP, US-NCAP, IIHS,FMVSS 208) by way of which the longitudinal shaft assembly is compressed(shortened) in the axial direction, firstly the optionally presentdisplacement distance of the constant velocity joint, or of the constantvelocity joints, respectively, is initially completely utilized suchthat all components of the longitudinal shaft assembly remain intact andfunctional. In the case of a further compression of the longitudinalshaft assembly the axial securing feature of the shaft connection isreleased upon reaching a release force, and a mutual displacement of theshafts into one another is performed.

The crash behaviour of the longitudinal shaft assembly is thuspreferably set primarily by way of a release force at which the releaseof the axial securing feature is performed and a mutual displacement ofthe first shaft and the second shaft arises. In the event of a crash, inparticular in the case of motor vehicles, a defined and pre-determineddeformation of the longitudinal shaft assembly can thus be set as afunction of a resulting crash force.

The explanations pertaining to the shaft connection can be applied tothe longitudinal shaft assembly and vice versa.

The objects set at the outset are furthermore achieved by a motorvehicle having a longitudinal shaft assembly proposed here.

By way of precaution, it is pointed out that the numerical words usedhere (“first”, “second”, “third”, . . . ) serve for distinction betweenseveral similar objects, dimensions or processes, that is to say they donot specify a dependency and/or sequence of said objects, dimensions orprocesses. If a dependency and/or sequence is necessary, this will beexplicitly stated here, or will emerge in a manner so understood by aperson skilled in the art from a study of the embodiment beingspecifically described.

BRIEF SUMMARY OF THE DRAWINGS

The present subject matter will be discussed in more detail below bymeans of the figures. It is pointed out that the invention is notintended to be restricted by the examples shown. In particular, unlessexplicitly presented otherwise, it is also possible for partial aspectsof the subject matter discussed in the figures to be extracted andcombined with other constituent parts and knowledge from the presentdescription and/or figures. The same reference signs are used to denoteidentical objects, such that, where appropriate, explanations from otherfigures can be taken into consideration in a supplementary manner In thefigures, in each case schematically:

FIG. 1 shows an example of a longitudinal shaft assembly;

FIG. 2 shows a known example of a shaft connection, in a lateralsectional view;

FIG. 3 shows an example of a shaft connection in an initial position, ina lateral sectional view;

FIG. 4 shows the shaft connection as per FIG. 3 in an assembly that iselongated in relation to the initial position, in a lateral sectionalview;

FIG. 5 shows the shaft connection as per FIG. 3 in an assembly that iscompressed in relation to the initial position, in a lateral sectionalview;

FIG. 6 shows a further example of a longitudinal shaft assembly;

FIG. 7 shows the further example of a shaft connection according to FIG.6 in an initial position, in a lateral sectional view;

FIG. 8 shows the further shaft connection as per FIG. 7 in an assemblythat is elongated in relation to the initial position, in a lateralsectional view; and

FIG. 9 shows the further shaft connection as per FIG. 7 in an assemblythat is compressed in relation to the initial position, in a lateralsectional view.

DESCRIPTION

FIG. 1 shows an example of a longitudinal shaft assembly 2 of a motorvehicle 3. The disposal of the longitudinal shaft assembly 2 in themotor vehicle 3 is performed so as to be parallel to the traveldirection of the motor vehicle 3, thus parallel to the axial direction10. The longitudinal shaft assembly 2 here is composed of a first shaft4 which has a first end 5 and a second end 6, and two second shafts 7together, by way of which the torques of the drive input of the motorvehicle 3 are transmitted. The first shaft 4 and the second shaft 7 formin each case a rigid shaft connection 1. The longitudinal shaft assembly2 herein by way of constant velocity rotary joints 27 is linked tofurther components of the motor vehicle 3, wherein the constant velocityrotary joints 27 possess a limited displacement range in the axialdirection 10. On account of the displacement range of the constantvelocity rotary joints 27, the movements of individual components of thelongitudinal shaft assembly 2 or of the motor vehicle 3 that arise inthe usual operation of the longitudinal shaft assembly 2 are compensatedfor in the longitudinal direction of the motor vehicle (the axialdirection 10). Moreover, torsioning of the longitudinal shaft assembly 2on account of the constant velocity rotary joints 27 in relation tofurther components of the motor vehicle 3 that also arises in theoperation are also equalized by deflecting the constant velocity joints27.

FIG. 2 shows a known example of a rigid shaft connection 1 in a lateralsectional view. The shaft connection 1 comprises a first shaft 4 havinga first end 5 and a second end 6, and a second shaft 7, disposed so asto be coaxial with the first shaft 4, having a first shaft end 8 and asecond shaft end 9; wherein the shafts 4, 7 extend along an axialdirection 10. The first end 5 of the first shaft 4 is connected in amaterially-integral manner to the first shaft end 8 of the second shaft7 by way of a friction-welded connection.

A constant velocity rotary joint 27 having a joint internal part 28, ajoint external part 29, and roller members 30 disposed therebetween isdisposed on the second shaft end 9 of the second shaft 7, said rollermembers 30 in the operation of the longitudinal shaft assembly 2 beingmutually disposed in a functional position 31. At the functionalposition 31 the mentioned components of the constant velocity rotaryjoint 27 are disposed in a mutual position in which the envisagedfunction of the constant velocity rotary joint 27 is provided (thus thetransmission of torques at a constant velocity of the shafts connectedby way of the constant velocity rotary joint 27, optionally whiledeflecting; here the axial displacement of the joint internal part 28 inrelation to the joint external part 29 along the axial direction 10because the constant velocity rotary joint 27 is a constant velocitydisplacement joint). The functional position 31 is not present when thecomponents, for example in the event of a crash, have been moved out ofsaid position and a constant velocity of the shafts connected by way ofthe constant velocity rotary joint 27 (here the joint external part 29and the joint internal part 28) is no longer guaranteed specifically inthe case of deflection of the shafts.

In the event of a crash by way of which the longitudinal shaft assembly2, and/or the shaft connection 1, is compressed (shortened) in the axialdirection 10 (see compression 21), firstly the displacement distance ofthe constant velocity rotary joint 27 is initially completely utilizedsuch that all components of the longitudinal shaft assembly 2 remainintact and functional. In the case of a further compression of thelongitudinal shaft assembly 2, or of the shaft connection, respectively,the first shaft 4, or the second shaft 7, respectively, is deformed,wherein mutual guiding of the shafts 4, 7 is no longer guaranteed.Furthermore, any elongation 20 of the shaft connection 1 is not possiblewithout mutual guiding of the shafts 4, 7 (see joint external part 29)being sacrificed, here upon exceeding the displacement distance of theconstant velocity (displacement) joint 27.

FIG. 3 shows an example of a shaft connection 1 in an initial position14 in a lateral sectional view. The shaft connection 1 has a first shaft4 having a first end 5 and a second end 6, and a second shaft 7,disposed so as to be coaxial with the first shaft 4, having a firstshaft end 8 and a second shaft end 9, wherein the shafts 4, 7 extendalong an axial direction 10. The first end 5 of the first shaft 4 formsa hollow portion 11, wherein the first shaft end 8 of the second shaft 7forms a first journal 12 having a displacement portion 13. At least inan initial position 14 of the shaft connection 1, the first shaft end 8extends through the hollow portion 11, and the hollow portion 11 by wayof the displacement portion 13 along the axial direction 10 forms aguide portion 40 and in a circumferential direction 15 a form-fittingfirst connection 16. In the initial position 14 which is present in theoperation of the shaft connection 1 in an installed condition, forexample as part of a longitudinal shaft assembly 2 in a motor vehicle 3or on a testbed, a mutual displacement 17 of the first shaft 4 and thesecond shaft 7 along the axial direction 10 is prevented by an axialsecuring feature 18. In an (actual or only simulated) event of a crash,the axial securing feature 18 is releasable by way of a release force 19that acts in the axial direction 10 (see FIGS. 4 and 5), and the firstshaft 4 is displaceable along the axial direction 10 in relation to thesecond shaft 7. Proceeding from the initial position 14, guiding by theguide portion 40 is guaranteed in the case of an elongation 20 (see FIG.4) as well as in the case of a compression 21 (see FIG. 5) of the shaftconnection 1.

Proceeding from the initial position 14, the form-fitting firstconnection 16 over a distance 22 is (at least partially) guaranteed inthe case of the elongation 20 as well as in the case of the compression21 of the shaft connection 1. The form-fitting first connection 16 isformed by a spline toothing 23 that is configured on the displacementportion 13 and on the hollow portion 11.

The second shaft 7, proceeding from the displacement portion 13 towardsthe second shaft end 9, has a journal portion 24 that extends along theaxial direction 10, wherein a largest diameter 25 of the journal portion24 is smaller than a smallest diameter 26 of the hollow portion 11. Thisexample of the journal portion 24 enables the second shaft 7 to be ableto be pushed further into the first shaft 4 so that the hollow portion11 by way of the journal portion 24 guarantees mutual guiding of theshafts 4, 7 (see FIG. 5). Mutual guiding of the first shaft 4 and thesecond shaft 7 thus continues to be guaranteed in the case of a furthercompression 21 of the shaft connection 1, even when the form-fittingfirst connection 16 is no longer present.

A constant velocity rotary joint 27 having a joint internal part 28, ajoint external part 29, and roller members 30 disposed therebetween isdisposed on the second shaft end 9 of the second shaft 7, said rollermembers 30 in the operation of the shaft connection 1 being mutuallydisposed in a functional position 31. A release force 19 required hereinfor releasing the axial securing feature 18 is lower than a force 32which is required for releasing the functional position 31.

The shaft connection 1 is designed such that in the event of a crash theaxial securing feature 18 is initially released and releasing of thefunctional position 31 of the constant velocity rotary joint 27 isperformed only thereafter. The mutual guiding of the shafts 4, 7 canthus be guaranteed specifically in the case of an elongation 20 of theshaft connection 1 and also in the case of a compression 21, without theprovided constant velocity rotary joints 27 having to be equipped with acorrespondingly greater displacement capability.

The axial securing feature 18 comprises an elastically deformablesecuring ring 33 which in the initial position 14 is positioned in afirst groove 34 that is disposed in the hollow portion 11 and isembodied so as to be encircling in the circumferential direction 15 andin a second groove 35 that is disposed in the displacement portion 13and is embodied so as to be encircling in the circumferential direction15 such that the securing ring 33 in the axial direction 10 forms aform-fitting second connection 36 of the first shaft 4 to the secondshaft 7.

When assembling the second shaft 7 in the first shaft 4, the securingring 33 is disposed in the second groove 35 and is then, conjointly withthe displacement portion 13, introduced into the hollow portion 11. Thesecuring ring 33 is elastically deformed herein and slides along theinternal circumferential face of the hollow portion 11 until the initialposition 14 is reached. The deformation of the securing ring 33 isreversed in this mutual position of the shafts 4, 7, and said securingring 33 is now additionally disposed in the first groove 34 such that aform-fitting second connection 36 of the shafts 4, 7 is formed.

The hollow portion 11, proceeding from the first end 5 of the firstshaft 4 towards the second end 6, along the axial direction 10 extendsfrom a first hollow portion end 37 to a second hollow portion end 38,wherein the first groove 34 is disposed on the second hollow portion end38.

An annular seal 39 is disposed on the first hollow portion end 37,wherein the annular seal 39 in the initial position 14, conjointly withthe second shaft 7, effects sealing of the first shaft 4. The annularseal 39 is positioned in a third groove 41 that is disposed in thedisplacement portion 13.

The first shaft 4 is a hollow shaft having a cavity 42 that adjoins thehollow portion 11, wherein the second shaft 7 in the case of acompression 21 of the shaft connection 1 extends into the cavity 42 (seeFIG. 5).

FIG. 4 shows the shaft connection 1 as per FIG. 3 in an assembly that iselongated in relation to the initial position 14, in a lateral sectionalview. Reference is made to the explanations pertaining to FIG. 3. Asopposed to FIG. 3, the shaft connection 1 here is illustrated after anelongation 20, thus a displacement 17 of the second shaft 7 in relationto the first shaft 4, and an extension of the shaft connection 1. Theaxial securing feature 18 has been released by a release force 19 actingin the axial direction 10, and the first shaft 4 has been displacedalong the axial direction 10 in relation to the second shaft 7. Thefirst shaft end 8 is still disposed in the hollow portion 11 of thefirst shaft 4 also in the case of this elongation 20 proceeding from theinitial position 14 of the shaft connection 1. The hollow portion 11 byway of the displacement portion 13 along the axial direction 10 forms aguide portion 40 and in a circumferential direction 15 a form-fittingfirst connection 16. Proceeding from the initial position 14, guiding bythe guide portion 40 is also guaranteed even in the case of theelongation 20 of the shaft connection 1.

As is shown in FIG. 3, the form-fitting first connection 16 in theinitial position 14 has a length 45 in the axial direction 10. Thedisplacement portion 13 is at least partially moved out of the hollowportion 11 in the case of an elongation 20 of the shaft connection 1 bythe displacement 17. On account of the displacement portion 13 whichalong the axial direction 10 extends across a larger length than thehollow portion 11, the form-fitting first connection 16 can bemaintained even in the case of an elongation 20 of the shaft connection1. By way of the displacement portion 13 it is guaranteed that thelength 45 (here also comprising the securing ring 33) of theform-fitting first connection 16 present in the initial position 14 isat least partially maintained even in the case of an elongation 20 ofthe shaft connection 1 by a displacement 17 proceeding from the firstinitial position 14.

FIG. 5 shows the shaft connection 1 as per FIG. 3 in an assembly that iscompressed in relation to the initial position 14, in a lateralsectional view. Reference is made to the explanations pertaining to FIG.3. As opposed to FIG. 3, the shaft connection 1 here is illustratedafter a compression 21, thus a displacement 17 of the second shaft 7 inrelation to the first shaft 4 and a shortening of the shaft connection1. The axial securing feature 18 has been released by a release force 19that acts in the axial direction 10, and the first shaft 4 has beendisplaced along the axial direction 10 in relation to the second shaft7. In the case of this compression 20, proceeding from the initialposition 14 of the shaft connection 1 or from the elongation 21according to FIG. 4, which has already arisen previously, the firstshaft end 8 is disposed within the cavity 42 of the first shaft 4, andthe journal portion 24 of the second shaft 7 is disposed in the hollowportion 11 of the first shaft 4. The first shaft 4 here is guided alongthe axial direction 10 by way of the hollow portion 11 and the journalportion 24. The form-fitting first connection 16 is not present here.Proceeding from the initial position 14, on account of the interactionof the journal portion 24 and the hollow portion 11, guiding is alsostill guaranteed in the case of the heavy compression 21 of the shaftconnection 1 present here.

The crash behaviour of the longitudinal shaft assembly 2 or of the shaftconnection 1, respectively, is thus preferably set primarily by way of arelease force 19 at which the release of the axial securing feature 18is performed and a mutual displacement 17 of the first shaft 4 and thesecond shaft 7 arises. In the event of a crash, in particular in thecase of motor vehicles 3, a defined and pre-determined deformation ofthe longitudinal shaft assembly 2 can thus be set as a function of anarising crash force.

FIG. 6 shows a further example of a longitudinal shaft assembly 2 of amotor vehicle 3. Reference is made to the explanations pertaining toFIG. 1. The longitudinal shaft assembly 2 is composed of a first shaft 4which has a first end 5 and a second end 6, and two second shafts 7 byway of which the torques of the drive input of the motor vehicle 3 aretransmitted. The first shaft 4 and the second shaft 7 form in each caseone rigid shaft connection 1.

FIG. 7 shows the further example of a shaft connection 1 according toFIG. 6 in an initial position 14, in a lateral sectional view. FIG. 8shows the further shaft connection 1 as per FIG. 7 in an assembly thatis elongated in relation to the initial position 14, in a lateralsectional view. FIG. 9 shows the further shaft connection 1 as per FIG.7 in an assembly that is compressed in relation to the initial position14, in a lateral sectional view. FIGS. 7 to 9 are collectively describedhereunder. Reference is made to the explanations pertaining to FIGS. 3to 5 and FIG. 6.

As opposed to the example according to FIGS. 3 to 5, the shaftconnection 1 on the second shaft 7 in the region of the first shaft end8 has a detent 43 which for delimiting the mutual displacement 17 in thecase of an elongation 20 of the shaft connection (see FIG. 8) interactswith a second hollow portion end 38 of the first shaft 7. As has alreadybeen shown in FIG. 3, the form-fitting first connection 16 in theinitial position 14 in the axial direction 10 has a length 45 (it istaken into account here that the securing ring 33 that forms the secondconnection 36 does not form a form-fitting first connection 16 that actsin the circumferential direction 15). In the case of an elongation 20 ofthe shaft connection 1 the displacement portion 13 is at least partiallymoved out of the hollow portion 11. The form-fitting first connection 16herein is maintained on account of the displacement portion 13 whichalong the axial direction 10 extends across a larger length than thehollow portion 11. By way of the displacement portion 13 it isguaranteed that the length 45 (here not comprising the securing ring 33)of the form-fitting first connection 16 present in the initial position14 is maintained even in the case of an elongation 20 of the shaftconnection 1 by a displacement 17 proceeding from the initial position14.

In the case of an elongation 20 of the shaft connection 1, the detent 43on the second shaft 7, conjointly with the first shaft 4, delimits anyfurther elongation 20 of the shaft connection 1. It can thus beprevented that the second shaft 7 can be completely removed from thehollow portion 11 of the first shaft 4. It is furthermore thus alsoprevented that the form-fitting first connection 16 can be (completely)released in the case of an elongation 20.

The detent 43 is formed by a detent diameter 44 which is larger than thesmallest diameter 26 of the hollow portion 11, or is larger than asmallest diameter 26 of the first shaft 4 in the region of the secondhollow portion end 38.

LIST OF REFERENCE SIGNS

1 Shaft connection2 Longitudinal shaft assembly3 Motor vehicle4 First shaft

5 First end 6 Second end

7 Second shaft8 First shaft end9 Second shaft end10 Axial direction11 Hollow portion12 First journal13 Displacement portion14 Initial position15 Circumferential direction16 First connection

17 Displacement

18 Axial securing feature19 Release force

20 Elongation 21 Compression 22 Distance

23 Spline toothing24 Journal portion25 Largest diameter26 Smallest diameter27 Constant velocity rotary joint28 Joint internal part29 Joint external part30 Roller members31 Functional position

32 Force

33 Securing ring34 First groove35 Second groove36 Second connection37 First hollow portion end38 Second hollow portion end39 Annular seal40 Guide portion41 Third groove

42 Cavity 43 Detent

44 Detent diameter

45 Length

1. A shaft connection for a longitudinal shaft assembly of a motorvehicle, comprising: at least one first shaft having a first end and asecond end, and a second shaft, disposed so as to be coaxial with thefirst shaft, having a first shaft end and a second shaft end; whereinthe first and second shafts extend along an axial direction; wherein thefirst end forms a hollow portion; wherein the first shaft end forms afirst journal having a displacement portion; wherein the first shaft endat least in an initial position of the shaft connection extends throughthe hollow portion, and the hollow portion by way of the displacementportion along the axial direction forms a guide portion and in acircumferential direction forms a form-fitting first connection; whereinin the initial position a mutual displacement of the first shaft and thesecond shaft, along the axial direction, is prevented by an axialsecuring feature; wherein in the event of a crash the axial securingfeature is releasable by way of a release force that acts in the axialdirection, and the first shaft is displaceable along the axial directionin relation to the second shaft; wherein, proceeding from the initialposition, guiding by the guide portion is guaranteed in the case of anelongation as well as in the case of a compression of the shaftconnection. 2.-15. (canceled)
 16. The shaft connection according toclaim 1, wherein, proceeding from the initial position, the form-fittingfirst connection in the case of an elongation as well as in the case ofa compression of the shaft connection is guaranteed at least over adistance of 20 millimeters.
 17. The shaft connection according to claim1, wherein the form-fitting connection is formed by a spline toothing onthe displacement portion and on the hollow portion.
 18. The shaftconnection according to claim 1, wherein the form-fitting firstconnection in the initial position has a length in the axial direction,wherein it is guaranteed in the case of an elongation of the shaftconnection by a displacement of at least 20 millimeters across thedisplacement portion that the length of the first connection ismaintained to the extent of at least 20% of the length in the axialdirection.
 19. The shaft connection according to claim 1, wherein thesecond shaft, proceeding from the displacement portion towards thesecond shaft end, has a journal portion that extends along the axialdirection, wherein a largest diameter of the journal portion is smallerthan a smallest diameter of the hollow portion.
 20. The shaft connectionaccording to claim 1, wherein the second shaft in the region of thefirst shaft end has a detent which for delimiting the mutualdisplacement in the case of an elongation of the shaft connectioninteracts with the first shaft.
 21. The shaft connection according toclaim 1, wherein a constant velocity rotary joint having a jointinternal part, a joint external part, and roller members disposedtherebetween is disposed on the second shaft end, said roller members inthe operation of the shaft connection being mutually disposed in afunctional position; and wherein a release force required for releasingthe axial securing feature is lower than a force which is required forreleasing the functional position.
 22. The shaft connection according toclaim 1, wherein the axial securing feature comprises an elasticallydeformable securing ring which in the initial position is positioned ina first groove that is disposed in the hollow portion and in a secondgroove that is disposed in the displacement portion such that thesecuring ring in the axial direction forms a form-fitting secondconnection of the first shaft to the second shaft.
 23. The shaftconnection according to claim 22, wherein the hollow portion, proceedingfrom the first end of the first shaft and towards the second end,extends along the axial direction from a first hollow portion end to asecond hollow portion end, and the first groove is disposed on thesecond hollow portion end.
 24. The shaft connection according to claim1, wherein the hollow portion, proceeding from the first end of thefirst shaft and towards the second end, extends along the axialdirection from a first hollow portion end to a second hollow portionend, and wherein an annular seal is disposed on the first hollow portionend, wherein the annular seal in the initial position, conjointly withthe second shaft, seals the first shaft.
 25. The shaft connectionaccording to claim 24, wherein the annular seal is positioned in a thirdgroove that is disposed in the displacement portion.
 26. The shaftconnection according to claim 1, wherein the axial securing feature inrelation to any compression of the shaft connection has a release forceof at most 30,000 Newtons.
 27. The shaft connection according to claim1, wherein the axial securing feature in relation to any elongation ofthe shaft connection has a release force of at most 120,000 Newtons. 28.A longitudinal shaft assembly for a motor vehicle, comprising: a shaftconnection including at least one first shaft having a first end and asecond end, and a second shaft, disposed so as to be coaxial with thefirst shaft, having a first shaft end and a second shaft end; whereinthe first and second shafts extend along an axial direction; wherein thefirst end forms a hollow portion; wherein the first shaft end forms afirst journal having a displacement portion; wherein the first shaft endat least in an initial position of the shaft connection extends throughthe hollow portion, and the hollow portion by way of the displacementportion along the axial direction forms a guide portion and in acircumferential direction forms a form-fitting first connection; whereinin the initial position a mutual displacement of the first shaft and thesecond shaft, along the axial direction, is prevented by an axialsecuring feature; wherein in the event of a crash the axial securingfeature is releasable by way of a release force that acts in the axialdirection, and the first shaft is displaceable along the axial directionin relation to the second shaft; wherein, proceeding from the initialposition, guiding by the guide portion is guaranteed in the case of anelongation as well as in the case of a compression of the shaftconnection.
 29. The longitudinal shaft assembly according to claim 28,wherein the first shaft at the second end is connected to a furthersecond shaft by way of a second shaft connection.